Question

Describe and compare multifactorial diseases and monogenic diseases in terms of heritability, genetic complexity, and study designs for studying them (one design for each is sufficient)

Answer 1

MUlTIFACTORIAL DISEASES

Researchers are learning that nearly all conditions and diseases have a genetic component. Some disorders, such as sickle cell disease and cystic fibrosis, are caused by mutations in a single gene. The causes of many other disorders, however, are much more complex. Common medical problems such as heart disease, diabetes, and obesity do not have a single genetic cause—they are likely associated with the effects of multiple genes in combination with lifestyle and environmental factors. Conditions caused by many contributing factors are called complex or multifactorial disorders.

Although complex disorders often cluster in families, they do not have a clear- cut pattern of inheritance. This makes it difficult to determine a person’s risk of inheriting or passing on these disorders. Complex disorders are also difficult to study and treat because the specific factors that cause most of these disorders have not yet been identified. Researchers continue to look for major contributing genes for many common complex dis

MONOGENIC DISEASES

Monogenic diseases are rare diseases attributable to genetic variants with large effects on disease status. Because of the high penetrance of such variants, the disease is typically inherited in a classical Mendelian fashion (e.g. dominant or recessive). The best-known monogenic respiratory diseases are CF and α1-antitrypsin deficiency, but hundreds of rare monogenic diseases affecting the respiratory system have been described. We refer the interested reader to the Online Mendelian Inheritance in Man (OMIM) website, which is a comprehensive, authoritative and continuously updated compendium of human genes and genetic phenotypes

COMPARISON

inheritance-

Monogenic autosomal dominant disorders occur through the inheritance of a single copy of a defective gene. Because these conditions are carried on the autosomes, males and females are equally affected

Multifactorial diseases are thought to result from complex interactions between genetic and environmental factors

Genetic Complexity-

Monogeniv Diseases

Complexity in monogenic diseases. Mutations in CFTR almost always cause the CF phenotype. Owing to modification effects by other genetic factors, the presence and nature of mutations at the CFTR locus cannot predict what the phenotypic manifestation of the disease will be.

Multifactorial diseases

Common medical problems such as heart disease, diabetes, and obesity do not have a single genetic cause—they are likely associated with the effects of multiple genes in combination with lifestyle and environmental factors. Conditions caused by many contributing factors are called complex or multifactorial disorders.

designs-

Monogenic conditions

Monogenic Disorder. Monogenic disorders are Mendelian disorders for which changes in a single gene are implicated in the disease process and that usually exhibit characteristic inheritance patterns (ie, additive, dominant, or recessive genetic models).